Electronegativity decreases down a group because the atomic radius increases and shielding increases due to electrons filling new principal energy levels, making the increased nuclear charge less significant. Therefore, iodine has a larger atomic radius and attracts electron density in a covalent bond less strongly than fluorine.

1. Electronegativity trends: down a group

2. Electronegativity trends: down a group
Electronegativity decreases down a group because:

3. Electronegativity trends: down a group
Electronegativity decreases down a group because:

4. Electronegativity trends: down a group
Electronegativity decreases down a group because:
1. The atomic radius increases.

5. Electronegativity trends: down a group
Electronegativity decreases down a group because:
1. The atomic radius increases.
2. Although the charge on the nucleus increases,
shielding also increases significantly. This is
because electrons added down the group fill new
principal energy levels.

6. Trends in electronegativity

7. Trends in electronegativity
Electronegativity of the halogens decreases down the group
due to an increase in atomic radius.

8. Trends in electronegativity
Electronegativity of the halogens decreases down the group
due to an increase in atomic radius.
Increased nuclear charge has no significant effect because
there are more electron shells and more shielding. Iodine
atoms therefore attract electron density in a covalent bond
less strongly than fluorine.

9. Trends in electronegativity
Electronegativity of the halogens decreases down the group
due to an increase in atomic radius.
Increased nuclear charge has no significant effect because
there are more electron shells and more shielding. Iodine
atoms therefore attract electron density in a covalent bond
less strongly than fluorine.
fluorine
atomic radius = 42 × 10-12 m
electronegativity = 4.0

10. Trends in electronegativity
Electronegativity of the halogens decreases down the group
due to an increase in atomic radius.
Increased nuclear charge has no significant effect because
there are more electron shells and more shielding. Iodine
atoms therefore attract electron density in a covalent bond
less strongly than fluorine.
fluorine iodine
atomic radius = 42 × 10-12 m atomic radius = 115 × 10-12 m
electronegativity = 4.0 electronegativity = 2.5